1. Field
Embodiments relate to a touch screen panel provided in an image display device.
2. Description of the Related Art
A touch screen panel is an input device. The touch screen panel enables a person to select an instruction with his/her finger or a tool. The touch screen panel also enables a person to input a user command. The instruction is displayed on a screen of an image display device.
The touch screen panel is provided in a front face of the image display device. The touch screen panel converts a contact position on the screen into an electrical signal from a finger or a tool that directly contacts the screen. Thus, an instruction selected at the contact position is input to the device as an input signal.
The touch screen panel may increase a range of applications because the touch screen panel can be a substitute for a separated input device. The separated input device may be a keyboard and a mouse, coupled to an image display device.
Known touch screen panels include a resistive touch screen panel, a capacitive touch screen panel, and an infrared touch screen panel.
A capacitive touch screen panel converts a contact position into an electric signal by sensing change of electrostatic capacity. The change of electrostatic capacity is generated by a conductive sensing pattern in association with other sensing patterns or a ground electrode. The conductive sensing pattern, in association with other sensing patterns or a ground electrode, occurs when a finger or an object contacts the touch screen.
The capacitive touch screen panel includes a plurality of sensing patterns connected to each other in a first direction and a plurality of sensing patterns connected to each other in a second direction crossing the first direction to obtain a coordinate of a contact position.
In a normal image display device, a transversal length is different from a longitudinal direction, so that the touch sensitivity in the first direction may be different from the touch sensitivity in the second direction.
In a normal image display device, the touch sensitivity is determined by a ratio between base capacitance and touch capacitance. The touch sensitivity is improved as the base capacitance is small and the touch capacitance is large. Therefore, when the transversal length of the screen is different from the longitudinal length, sensing patterns in a long side are connected to each other more than those in a short side. Thus, the base capacitance is increased so that the touch sensitivity is lowered.